Botulinum neurotoxins (BoNTs), synthesized by the Gram-positive, soil-dwelling bacterium Clostridium botulinum, are the most toxic substances known to humankind and are the causative agents of the neuroparalytic disease botulism (Johnson E (2005) in Topley and Wilson's microbiology and microbial infections, ed S. P. Borriello, P. R. Murray, and G. Funke (Hodder Arnold, London, United Kingdom), pp 1035-1088). Seven immunologically distinct serotypes of BoNTs designated A through G have been described (Gimenez D F & Gimenez J A (1995) Int J Food Microbiol 27: 1-9). BoNTs are initially synthesized as a single-chain polypeptide of ˜150 kDa, but posttranslational proteolytic cleavage yields distinct heavy and light chains (HC and LC) of ˜100 kDa and ˜50 kDa linked by a disulfide bond. The HC is further functionally divided into the HCC and HCN sub-domains. The HCC domain is responsible for recognition and binding to specific neuronal cell surface receptors leading to endocytosis, while the HCN domain is responsible for channel formation in the endocytic vesicle membrane and translocation and internalization of the LC across the endosomal membrane (Montecucco et al., (2004) Trends Microbiol 12: 442-446; Fischer A & Montal M (2007) J Biol Chem 282: 29604-29611; Fischer A, et al (2009) Proc Natl Acad Sci USA 106: 1330-1335). After translocation, the disulfide bond is cleaved, and the LC is released into the cell cytosol and refolded to the active enzyme component as a zinc-dependent endopeptidase (Fischer et al., supra; Fischer A & Montal M (2007) Proc Natl Acad Sci USA 104: 10447-10452; Pirazzini, et al., Cell Rep 2014, 8, 1870-1878). The LC then specifically targets and cleaves an intracellular SNARE protein at the pre-synaptic vesicles, which leads to inhibition of neurotransmitter release. Each BoNT serotype has a distinct cleavage target, with BoNT/A and E cleaving SNAP-25 at distinct sites, BoNT/B, D, F, and G cleaving VAMP/synaptobrevin at different sites, and BoNT/C cleaving both SNAP-25 and syntaxin (reviewed in Montecucco C & Schiavo G (1994) Mol Microbiol 13: 1-8).
BoNT/A and to a much lesser extent BoNT/B are used as unique and important pharmaceuticals to treat a variety of neuromuscular disorders and in cosmetics. Conditions for which the Food and Drug Administration approved the use of BoNTs include cosmetic treatments and to temporarily relieve a variety of muscle spasticity disorders, hyperhydrosis and migraines (Chaddock J A & Acharya K R (2011) FEBS J 278: 899-904). Cosmetic and clinical applications of BoNTs are increasing, and new formulations of BoNTs for pharmaceutical purposes are being developed necessitating clinical trials, accurate potency determination, and neutralizing antibody screening. For example, BoNTs are pharmaceutically administered for the treatment of pain disorders, voluntary muscle strength, focal dystonia, including cervical, cranial dystonia, and benign essential blepharospasm, hemifacial spasm, and focal spasticity, gastrointestinal disorders, hyperhidrosis, and cosmetic wrinkle correction, Blepharospasm, oromandibular dystonia, jaw opening type, jaw closing type, bruxism, Meige syndrome, lingual dystonia, apraxia of eyelid, opening cervical dystonia, antecollis, retrocollis, laterocollis, torticollis, pharyngeal dystonia, laryngeal dystonia, spasmodic dysphonia/adductor type, spasmodic dysphonia/abductor type, spasmodic dyspnea, limb dystonia, arm dystonia, task specific dystonia, writer's cramp, musician's cramps, golfer's cramp, leg dystonia, thigh adduction, thigh abduction knee flexion, knee extension, ankle flexion, ankle extension, equinovarus, deformity foot dystonia, striatal toe, toe flexion, toe extension, axial dystonia, pisa syndrome, belly dancer dystonia, segmental dystonia, hemidystonia, generalised dystonia, dystonia in lubag, dystonia in corticobasal degeneration, dystonia in lubag, tardive dystonia, dystonia in spinocerebellar ataxia, dystonia in Parkinson's disease, dystonia in Huntington's disease, dystonia in Hallervorden-Spatz disease, dopa-induced dyskinesias/dopa-induced dystonia, tardive dyskinesias/tardive dystonia, paroxysmal dyskinesias/dystonias, kinesiogenic non-kinesiogenic action-induced palatal myoclonus, myoclonus myokymia, rigidity, benign muscle cramps, hereditary chin trembling, paradoxic jaw muscle activity, hemimasticatory spasms, hypertrophic branchial myopathy, maseteric hypertrophy, tibialis anterior hypertrophy, nystagmus, oscillopsia supranuclear gaze palsy, epilepsia, partialis continua, planning of spasmodic torticollis operation, abductor vocal cord paralysis, recalcitant mutational dysphonia, upper oesophageal sphincter dysfunction, vocal fold granuloma, stuttering Gilles de la Tourette syndrome, middle ear myoclonus, protective larynx closure, postlaryngectomy, speech failure, protective ptosis, entropion sphincter Odii dysfunction, pseudoachalasia, nonachalsia, oesophageal motor disorders, vaginismus, postoperative immobilisation tremor, bladder dysfunction, detrusor sphincter dyssynergia, bladder sphincter spasm, hemifacial spasm, reinnervation dyskinesias, cosmetic use craw's feet, frowning facial asymmetries, mentalis dimples, stiff person syndrome, tetanus prostate hyperplasia, adipositas, treatment infantile cerebral palsy strabismus, mixed paralytic concomitant, after retinal detachment surgery, after cataract surgery, in aphakia myositic strabismus, myopathic strabismus, dissociated vertical deviation, as an adjunct to strabismus surgery, esotropia, exotropia, achalasia, anal fissures, exocrine gland hyperactivity, Frey syndrome, Crocodile Tears syndrome, hyperhidrosis, axillar palmar plantar rhinorrhea, relative hypersalivation in stroke, in Parkinsosn's, in amyotrophic lateral sclerosis, spastic conditions, in encephalitis and myelitis autoimmune processes, multiple sclerosis, transverse myelitis, Devic syndrome, viral infections, bacterial infections, parasitic infections, fungal infections, in hereditary spastic paraparesis postapoplectic syndrome hemispheric infarction, brainstem infarction, myelon infarction, in central nervous system trauma, hemispheric lesions, brainstem lesions, myelon lesion, in central nervous system hemorrhage, intracerebral hemorrhage, subarachnoidal hemorrhage, subdural hemorrhage, intraspinal hemorrhage, in neoplasias, hemispheric tumors, brainstem tumors, and myelon tumor.
BoNT with optimized properties for the particular condition being treated or other usage are needed.